Continuity of care for patients who transition between health care settings is vitally important for maintaining quality health care. Nursing home (NH) residents experience a high rate of hospitalizations, including those with chronic conditions such as atrial fibrillation (AFIB). High quality medication use across settings of care is a key component of care coordination. However, NH residents with AFIB are at risk for adverse drug events, as pharmacotherapeutic management of AFIB, especially the use of warfarin, can be problematic among older adults. The relationship between medication quality and transitions to the hospital in the NH AFIB population is unclear, as most research on medication continuity across care settings focuses on the transition of patients between the hospital and community. The objective of this application is to examine the relationship between quality of pharmacotherapeutic management and transitions between the NH and hospital among long-stay NH residents with AFIB. The proposed study has three specific aims: 1) To describe pharmacotherapeutic management of AFIB in the nursing home; 2) To characterize changes in antithrombotic medication use surrounding transitions experienced by NH residents with AFIB; 3) To determine the relationship between quality of AFIB medication use and hospital transitions among long-stay NH residents with AFIB. Analyses will be performed through linkage of the 2006-2009 Minimum Dataset with Medicare administrative claims and Online Survey Certification and Reporting data. The first two aims will use a cross-sectional cohort of NH residents with AFIB; the third aim will use a nonconcurrent prospective cohort design with repeated measures. The research training program will support the development of expertise in analytic methods, specifically the cross-lagged panel model, that are new to the field of health services research. Training provided by this fellowship award will facilitate the applicant in adapting this method to address future questions regarding medication reconciliation between the hospital and NH. The proposed research on AFIB medication quality in NHs and the relationship between AFIB medication use and transitions addresses the mission and research priorities of the National Institute on Aging by focusing on AFIB, a chronic condition common among older adults, and by addressing the relationship between management of this condition and outcomes such as hospitalizations. Providing information on the potential bidirectional influences of medication quality and hospitalizations among NH residents will support the development of interventions that promote high quality continuity of care, especially with respect to pharmacotherapy, for NH residents moving across settings of care.